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Cholesteric Liquid Crystal (cholesteric + liquid_crystal)
Selected AbstractsPhototunable Azobenzene Cholesteric Liquid Crystals with 2000 nm RangeADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Timothy J. White Abstract Phototuning of more than 2000,nm is demonstrated in an azobenzene-based cholesteric liquid crystal (azo-CLC) consisting of a high-helical-twisting-power, axially chiral bis(azo) molecule (QL76). Phototuning range and rate are compared as a function of chiral dopant concentration, light intensity, and thickness. CLCs composed of QL76 maintain the CLC phase regardless of intensity or duration of exposure. The time necessary for the complete restoration of the original spectral properties (position, bandwidth, baseline transmission, and reflectivity) of QL76-based CLC is dramatically reduced from days to a few minutes by polymer stabilization of the CLC helix. [source] Bottom-Up Fabrication of Photonic Defect Structures in Cholesteric Liquid Crystals Based on Laser-Assisted Modification of the Helix,ADVANCED MATERIALS, Issue 9 2007H. Yoshida Controlled fabrication of defect structures is performed in cholesteric liquid crystals by a laser-assisted polymerization process that induces a local elongation of the helix (see figure). Low-threshold laser action is observed from the photonic defect-mode observed within the selective reflection band. [source] Phototunable Azobenzene Cholesteric Liquid Crystals with 2000 nm RangeADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Timothy J. White Abstract Phototuning of more than 2000,nm is demonstrated in an azobenzene-based cholesteric liquid crystal (azo-CLC) consisting of a high-helical-twisting-power, axially chiral bis(azo) molecule (QL76). Phototuning range and rate are compared as a function of chiral dopant concentration, light intensity, and thickness. CLCs composed of QL76 maintain the CLC phase regardless of intensity or duration of exposure. The time necessary for the complete restoration of the original spectral properties (position, bandwidth, baseline transmission, and reflectivity) of QL76-based CLC is dramatically reduced from days to a few minutes by polymer stabilization of the CLC helix. [source] An Optically Active Polythiophene Exhibiting Electrochemically Driven Light-Interference ModulationADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Hiromasa Goto Abstract Optically active polythiophene (PT*) is successfully prepared by electrochemical polymerization using a cholesteric liquid crystal (CLC) electrolyte solution. Polarizing optical microscopy observations of the polymer reveal a well-resolved fingerprint texture similar to the optical texture of the CLC. Circular dichroism measurements indicate a Cotton effect. The PT* film produced by the asymmetric polymerization in CLC exhibits a variable diffraction function, electrochemically driven refractive index modulation, and electrochromism originating from the periodic dielectric structure, representing a form of structural electrochromism. [source] Glass-Forming Cholesteric Liquid Crystal Oligomers for New Tunable Solid-State LaserADVANCED MATERIALS, Issue 8 2010Seiichi Furumi A new potential utility of glass-forming cholesteric liquid crystal (G-CLC) oligomers for application in tunable solid-state laser is presented. The G-CLC is capable of tuning the photonic band gaps (PBGs) by way of the annealing temperature and preserving the tuned PBGs by a subsequent supercooling treatment. This G-CLC film enables the facile fabrication of a continuously gradated PGB structure and, thus, the continuous tuning of a single laser-emission peak (see figure). [source] Localization and imaging of local shunts in solar cells using polymer-dispersed liquid crystalsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2001Jan Schmidt An easy-to-use technique for the localization and imaging of local shunts in solar cells is introduced. The method is based on temperature-sensitive polymer-dispersed cholesteric liquid crystal foils, covering the reverse-biased solar cell. The unique optical properties of the cholesteric liquid crystal, known as selective reflection, render the local shunts of a solar cell visible as a color distribution in the foil, which is directly correlated with the spatial shunt distribution. The novel method is applied to several laboratory and commercial silicon solar cells and its high sensitivity is demonstrated. Copyright © 2001 John Wiley & Sons, Ltd. [source] 3D Bi-chiral Photonic Crystals: Three-Dimensional Bi-Chiral Photonic Crystals (Adv. Mater.ADVANCED MATERIALS, Issue 46 200946/2009) Bi-chiral photonic crystals are tailored man-made solids inspired by blue-phase cholesteric liquid crystals. They possess two types of chirality, leading to four different types of bi-chiral structures. In naturally occurring blue-phase liquid crystals, only two of these are thermodynamically stable. On p. 4680, Michael Thiel and co-workers fabricate all four via direct laser writing. [source] Bottom-Up Fabrication of Photonic Defect Structures in Cholesteric Liquid Crystals Based on Laser-Assisted Modification of the Helix,ADVANCED MATERIALS, Issue 9 2007H. Yoshida Controlled fabrication of defect structures is performed in cholesteric liquid crystals by a laser-assisted polymerization process that induces a local elongation of the helix (see figure). Low-threshold laser action is observed from the photonic defect-mode observed within the selective reflection band. [source] Electrochemical polymerization of pyrrole in cholesteric liquid crystals: Morphology and optical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2007Hiromasa Goto Abstract Electrochemical polymerization in a cholesteric liquid-crystal electrolyte was carried out. Polypyrrole thus synthesized in a cholesteric liquid-crystal electrolyte could be clearly seen to form a specific morphology. The polypyrrole films exhibited chiroptical properties and formed various surface structures such as Schlieren, Nazca-line, sea-anemone, and wire-loop structures. These structures that developed during polymerization were preserved even after washing. Moreover, no chiral molecule reacted chemically with the monomer during polymerization, and the electrolyte functioned only as a matrix chiral continuum. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1377,1387, 2007. [source] | ||||||||||